This invention relates to new and useful improvements in heating units such as, for example, a stove arranged for home use.
Many types of stoves have heretofore been provided for burning wood, coal and the like, and intended primarily to furnish heat to room areas.
Conventional stoves are notoriously inefficient room heaters because when used they draw much of the heated air up through the flue pipe for exit to the atmosphere. Most of the heat produced by the fire is thus transferred to the draft air which is promptly released to the outside atmosphere, rather than to the air contained within the building. In addition, because air is being withdrawn from the dwelling, creating a relatively low pressure therein, air is simultaneously drawn into the dwelling to replace it. It has been found that a direct supply of outside air to the stove diminishes energy losses because stove heated air is not removed, nor is there a constant influx of cold outside air into the interior of the building. Numerous device's exist in the prior art for extracting heat from a firebox. Some run tubes through the coals and burning material and discharge air through the tubes. Stoves of this type are represented in U.S. Pat. Nos. 195,104 and 4,166,444. The wood burning stoves commonly employed generally are extremely inefficient as heating sources. Most of them rely upon radiations and convection currents of air within the room coming into contact with the outside walls of the stove to produce heated air. In such stoves the major portion of the heat produced by the combustion of the wood or other combustible products in the stove is lost with the combustion products out the flue or smoke stack. This is one of the greatest drawbacks of self-contained room size wood burning stoves. In addition, the room itself is not uniformly heated. The region immediately adjacent the stove is too hot, while the more remote corners or sides of the room obtain relatively little heat from the stove.
Some early models of wood burning heating stoves, in attempts to overcome the inefficiency of such stoves, relied upon rather extensive baffles between the upper portion of the combustion chamber and the outlet for the flue in order to force the combustion products to take a tortuous path from the upper portion of the combustion chamber to the flue. This resulted in retention of more heat within the stove and an improvement in radiation of this heat from the stove. The operation, however, is still relatively inefficient and a large amount of heat loss results. Stoves of this type are shown in U.S. Pat. Nos. 585,027, 1,400,299, 2,238,345, 2,316,392, 2,789,554, 4,127,100, 4,129,251, 4,136,663 and 4,150,658.
Other early wood burning stove's had double walls along at least a portion of their fire chamber's to create an air chamber heated on one side by one of the walls of the fire chamber. An air inlet was provided near the bottom of the air chamber and appropriate air outlets were created near the top. Air rose by convection current through the air chamber and out the outlets. Thus, this air was heated in addition to the air coming in contact with the outside of the stove. Improved efficiency did result, but the bulk of the heat generated by the process of combustion was lost in the flue. Stoves of this type are represented in U.S. Pat. Nos. 128,989, 1,469,463, 2,345,329, 4,136,662 and 4,140,101.